Safety paper and method of making the same



Patented Mar. 16, 1937 UNIT SAFETY PAPER AND METHOD OF MAKING THE SAME Burgess W. Smith, Rochester, N. Y., assignor to The Todd Company, Inc., Rochester, N. Y., a corporation of New York No Drawing. Application August 22, 1932, Serial No. 629,890

2 Claims.

This invention relates to safety papers for making bank checks, drafts, bonds, or any other document in which it is desired that erasures made with, chemical ink eradicators be indicated by a stain or discoloration and to methods of making the same.

The object of my invention is to provide a more practical and efficient paper of this character, capable of being inexpensively manufactured in the desired commercial form and a more practical and efficient method of making the same. More particularly, it is the object of the invention to provide a paper which will be quickly and conspicuously discolored by the action of ink eradicator, regardless of the order of application of its components, or its acidity, and a method of making the same.

To these and other ends, the invention resides in certain improvements, combination of parts, and method steps,all of which will be more fully described, the novel features being pointed out, in the claims at the end of this specification.

In the preparation of the class of safety papers in which the use of ink eradicators produces a stain, the active ingredient, for maximum efliciency, should possess certain characteristics. The material should be relatively stable to normal influences, and the stain when produced should resist removal by reagents commonly known and used for this purpose. It should react with the commonly used ink eradicator, which is composed of an alkaline hypochlorite, generally hypochlorite of soda, used in combination with a second component consisting of a solution of tartaric acid. It should react in either acid or alkaline condition of the hypochlorite of soda or other eradicator.

I have found that compounds having two benzene rings united by the linkage -CH=CH- with at least one amino on each ring para to that linkage, such, for example, as diaminostilbene, its homolo-gues and analogues, will develop a conspicuous stain with hypochlorite of soda ink eradicators. in any order of application of their components, or in either alkaline or acid condition.

I prefer to use the sulio-nic acid inasmuch as it makes a concentrated solution in caustic soda, and may again be precipitated in a relatively insoluble form by the addition of acid and acid compounds.

In the use of this product in this way, I am enabled to introduce it into the paper in the beater or Jordan, or I may incorporate the aforesaid sodium salt of the sulfonic acid in the sizing, which in turn may be precipitated in the insoluble form by passing the web through a solution of alum, or suitable acid.

I may use such a compound in an ink prepared with any of the commercially known varnish mediums, or use a more novel medium which is a solution of cellulose nitrate in diethylene phthalate. Inks of this nature may be applied as a general surface coating, or used to form a warning word or symbol such as is described in my Patent No. 1,454,837.

The quantities and proportions used for this purpose depend entirely on the desired depth of stain or discoloration, and the application of this material involves no special skill not possessed by one familiar with this art.

Paper having incorporated therein or thereon organic compounds of the class outlined will indicate or show the application of the usual commercial eradicators by developing a conspicuous brownish red color that is extremely difficult if not impossible to remove without conspicuously defacing or destroying the paper.

This compound and its salts show more or less color, particularly the commercially available sulfonic acid, which is an intermediate in the manufacture of the stilbene series of dyes. For this reason, it is desirable, in event it is used for printing a warning indicia, to camouflage the same, as, for example, by the methods described and illustrated in my Patent No. 1,675,769.

While certain substances and methods have been referred to herein by me, and specifically described, it is to be understood that other closely related substances containing the linkage -CH=CH, are included in this invention, particularly the homologues and analogues of the compound named, and other methods of application of these compounds, as are Well understood by those skilled in this art, may be used without departing from the spirit of this invention.

It is to be further understood that the term paper containing means that the material may be on the surface alone, incorporated in a film intimately attached thereto, or in the body of the paper. The term safety paper means any paper or writing surface on which it is desired to indicate the application of a chemical ink eradicator by the production of a stain or discoloration.

I claim:

1. A method of making safety papercomprising the step of adding p,p'-diaminostilbene during or after the formation of the web for the purpose of producing, by its reaction, a visible indication of the use of an ink eradicator.

2. A safety paper containing p,p-diaminostilbene and adapted to develop a conspicuous stain upon the application thereto of a chemical ink eradicator.

, BURGESS W. SMITH. 

